U.S. patent application number 17/012980 was filed with the patent office on 2020-12-24 for techniques for controlling precursors in chemical deposition processes.
This patent application is currently assigned to Varian Semiconductor Equipment Associates, Inc.. The applicant listed for this patent is Varian Semiconductor Equipment Associates, Inc.. Invention is credited to Elaina Babayan, Jonathan Bakke, Vijay Venugopal, Sarah White.
Application Number | 20200399758 17/012980 |
Document ID | / |
Family ID | 1000005066631 |
Filed Date | 2020-12-24 |
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United States Patent
Application |
20200399758 |
Kind Code |
A1 |
Babayan; Elaina ; et
al. |
December 24, 2020 |
TECHNIQUES FOR CONTROLLING PRECURSORS IN CHEMICAL DEPOSITION
PROCESSES
Abstract
An apparatus for controlling precursor flow. The apparatus may
include a processor; and a memory unit coupled to the processor,
including a flux control routine. The flux control routine may be
operative on the processor to monitor the precursor flow and may
include a flux calculation processor to determine a precursor flux
value based upon a change in detected signal intensity received
from a cell of a gas delivery system to deliver a precursor.
Inventors: |
Babayan; Elaina;
(Gloucester, MA) ; White; Sarah; (Gloucester,
MA) ; Venugopal; Vijay; (Gloucester, MA) ;
Bakke; Jonathan; (Gloucester, MA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Varian Semiconductor Equipment Associates, Inc. |
Gloucester |
MA |
US |
|
|
Assignee: |
Varian Semiconductor Equipment
Associates, Inc.
Gloucester
MA
|
Family ID: |
1000005066631 |
Appl. No.: |
17/012980 |
Filed: |
September 4, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15946483 |
Apr 5, 2018 |
10822699 |
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17012980 |
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62611645 |
Dec 29, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 16/45544 20130101;
C23C 16/448 20130101; C23C 16/52 20130101; C23C 16/45553 20130101;
H01L 21/67253 20130101 |
International
Class: |
C23C 16/52 20060101
C23C016/52; C23C 16/448 20060101 C23C016/448; H01L 21/67 20060101
H01L021/67; C23C 16/455 20060101 C23C016/455 |
Claims
1. An apparatus for controlling precursor flow, comprising: an
ampoule to output a precursor; a sensor assembly communicatively
coupled to the source, and comprising: a cell, coupled to the
source, to receive and conduct the precursor; a detector, to detect
light transmitted through the cell; and a control system, the
control system arranged to determine a precursor flux value based
upon a change in detected light intensity received from the cell
during flow of the precursor through the cell, the control system
comprising: a temperature control processor, configured to:
determine a flux error value based upon the precursor flux value;
determine a temperature adjustment .DELTA.T, based upon the flux
error value; and calculate a new set of temperature setpoints to be
applied to the ampoule; and an end-of-life processor, the
end-of-life processor configured to: check for an end-of
ampoule-life condition when the new set of temperature setpoints is
not within the predetermined set of temperature limits.
2. The apparatus of claim 1, comprising a flux calculation
processor to determine the precursor flux value by: receiving a
first reference signal in the cell, generated at a first instance,
the first reference signal indicative of a detector performance at
the first instance for a detector, the detector to detect a light
intensity from a light source; receiving a background signal,
generated at the first instance, the background signal being
generated by the detector; receiving a second reference signal,
generated at a second instance, subsequent to the first instance,
the second reference signal indicative of the detector performance
at the second instance for the detector; and receiving a precursor
signal, generated at a third instance, subsequent to the first
instance, when the precursor is flowing in the cell.
3. The apparatus of claim 1, the temperature control processor
configured to: determine a warning band condition based upon the
precursor flux value; and adjust a temperature of the ampoule based
upon the warning band condition.
4. The apparatus of claim 1, the flux calculation processor
configured to calculate an integrated flux of the precursor by
determining the precursor flux value at a plurality of
instances.
5. The apparatus of claim 1, the temperature control processor
configured to adjust the temperature by: determining a temperature
adjustment .DELTA.T, where .DELTA.T=P* +D*d /dt+I*.intg. /dt, where
P, I and D are a proportional, integral, and derivative gains, and
where is an error based upon current temperature limits of the
ampoule.
6. The apparatus of claim 1 the temperature control processor
configured to adjust a temperature of the ampoule by: applying the
new set of temperature setpoints to control heating of the ampoule
when the new set of temperature setpoints are within a
predetermined set of temperature limits.
7. The apparatus of claim 1, the end-of-life processor configured
to: recalculate .DELTA.T to generate a conservative .DELTA.T based
upon a most conservative limit when the end-of ampoule life
condition has not been met; and calculate the new set of
temperature setpoints to be applied to the ampoule based upon the
conservative .DELTA.T.
8. The apparatus of claim 1, the flux control routine further
comprising an excursion processor, the excursion processor
configured to: determine a fault condition based upon the precursor
flux value; and send a notification signal of an excursion, when a
substrate being processed is during the fault condition is not a
first substrate.
9. The apparatus of claim 1, the flux control routine further
comprising a clog detection processor, the clog detection processor
configured to: receive a cell pressure reading for the cell;
receive the precursor flux value; and determine a clog location
based upon the cell pressure reading and precursor flux value.
10. A method of controlling precursor flow, comprising: measuring a
change in detected signal intensity in a cell of the gas delivery
system, caused by the flow of a precursor; determining a precursor
flux value based upon the change in the detected signal intensity;
determining a flux error value based upon the precursor flux value;
calculating a new set of temperature setpoints to be applied to the
ampoule; and checking for an end-of ampoule-life condition when the
new set of temperature setpoints is not within a predetermined set
of temperature limits.
11. The method of claim 10, wherein the measuring the change
comprises: receiving a first reference signal in the cell at a
first instance, the first reference signal indicative of a detector
performance at the first instance for a detector, the detector to
detect a light intensity from a light source; receiving a
background signal at the first instance, the background signal
being generated by the detector; receiving a second reference
signal at a second instance, subsequent to the first instance, the
second reference signal indicative of the detector performance at
the second instance for the detector; and receiving a precursor
signal from the detector at a third instance, subsequent to the
first instance, when the precursor is flowing in the cell and light
is generated by the light source.
12. The method of claim 10, wherein the providing the flow of the
precursor comprises providing a plurality of pulses at a plurality
of instances of the precursor, the method further comprising
calculating an integrated flux of the precursor based upon
determining the precursor flux value at the plurality of
instances.
13. The method of claim 10, further comprising: determining a
warning band condition based upon the precursor flux value; and
adjusting a temperature of the ampoule based upon the warning band
condition.
14. The method of claim 13, wherein the adjusting the temperature
comprises: determining a temperature adjustment .DELTA.T, where
.DELTA.T=P* +D*d /dt+I*.intg. /dt, where P, I and D are a
proportional, integral, and derivative gains, and where is an error
based upon current temperature limits of the ampoule.
15. The method of claim 13, wherein the adjusting the temperature
comprises: applying the new set of temperature setpoints to control
heating of the ampoule when the new set of temperature setpoints
are within the predetermined set of temperature limits.
16. The method of claim 15, wherein the adjusting the temperature
comprises: recalculating .DELTA.T to generate a conservative
.DELTA.T based upon a most conservative limit when the end-of
ampoule life condition has not been met; and calculating the new
set of temperature setpoints to be applied to the ampoule based
upon the conservative .DELTA.T.
17. The method of claim 10, further comprising: determining a fault
condition based upon the precursor flux value; and sending a
notification signal of an excursion, when a substrate being
processed is during the fault condition is not a first
substrate.
18. A method, comprising: determining a precursor flux value based
upon a change in detected signal intensity received from a cell of
a gas delivery system to deliver a precursor; determining a flux
error value based upon the precursor flux value; determining a
temperature adjustment .DELTA.T, based upon the flux error value;
calculating a new set of temperature setpoints to be applied to the
ampoule; and checking for an end-of ampoule-life condition when the
new set of temperature setpoints is not within the predetermined
set of temperature limits.
19. The method of claim 18, comprising determining the precursor
flux value by: receiving a first reference signal in the cell,
generated at a first instance, the first reference signal
indicative of a detector performance at the first instance for a
detector, the detector to detect a light intensity from a light
source; receiving a background signal, generated at the first
instance, the background signal being generated by the detector;
receiving a second reference signal, generated at a second
instance, subsequent to the first instance, the second reference
signal indicative of the detector performance at the second
instance for the detector; and receiving a precursor signal,
generated at a third instance, subsequent to the first instance,
when the precursor is flowing in the cell.
20. The method of claim 18, further comprising: applying the new
set of temperature setpoints to control heating of the ampoule when
the new set of temperature setpoints are within a predetermined set
of temperature limits.
Description
RELATED APPLICATIONS
[0001] This application is a continuation application to U.S.
Non-Provisional patent application Ser. No. 15/946,483, filed Apr.
5, 2018, entitled TECHNIQUES FOR CONTROLLING PRECURSORS IN CHEMICAL
DEPOSITION PROCESSES which claims priority to U.S. Provisional
Patent Application No. 62/611,645, filed Dec. 29, 2017, entitled
TECHNIQUES FOR CONTROLLING PRECURSORS IN CHEMICAL DEPOSITION
PROCESSES, both of which applications are incorporated by reference
herein in their entirety.
FIELD
[0002] The present embodiments relate to deposition processes, and
more particularly, to control of precursors in chemical deposition
processes.
BACKGROUND
[0003] In the present day, device fabrication, such as
semiconductor device fabrication may entail chemical deposition
processes to form thin layers with precise thickness control,
including over three dimensional structures. Such chemical
deposition processes include chemical vapor deposition (CVD) and
atomic layer deposition (ALD), among other processes.
[0004] Such chemical deposition processes may involve delivering
precursors from a solid source, gas source, or liquid source, such
as an ampoule. For example, the precursor may be delivered from an
ampoule to a process chamber, where the precursor reacts to form a
layer or sub-layer on a substrate. In present day apparatus, the
amount of precursor being delivered may not be properly
characterized, leading to variability in delivery of precursor
substrate-to-substrate, ampoule-to-ampoule, or over the lifetime of
an ampoule. Delay in detecting ampoule end of life can result in
significant amount of wafer (substrate) discard. As a precaution,
users may track carrier gas flow through an ampoule and may halt
the use of a precursor in an ampoule well before actual end of
life, resulting in a considerable portion of the ampoule fill being
unused, and causing higher overall cost.
[0005] With respect to these and other considerations the present
disclosure is provided.
SUMMARY
[0006] In one embodiment, an apparatus for controlling precursor
flow may include a processor, and a memory unit coupled to the
processor, including a flux control routine. The flux control
routine may be operative on the processor to monitor the precursor
flow. The flux control routine may include a flux calculation
processor to determine a precursor flux value based upon a change
in detected signal intensity received from a cell of a gas delivery
system to deliver a precursor.
[0007] In an additional embodiment, a method of controlling
precursor flow may include providing a flow of a precursor through
a gas delivery system, measuring a change in detected signal
intensity in a cell of the gas delivery system, caused by the flow
of the precursor, and determining a precursor flux value based upon
the change in detected signal intensity.
[0008] In another embodiment, an apparatus for controlling
precursor flow may include a source to output the precursor, and a
sensor assembly, communicatively coupled to the source. The sensor
assembly may include a cell, coupled to the source, to receive and
conduct the precursor, a light source, disposed on a first side of
the cell, to transmit light into the cell, and a detector, disposed
on a second side of the cell, opposite the light source, to detect
light transmitted through the cell. The apparatus may also include
a control system, the control system arranged to determine a
precursor flux value based upon a change in detected light
intensity received from the cell during flow of the precursor
through the cell.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A shows a system for chemical deposition, according to
embodiments of the disclosure;
[0010] FIG. 1B shows one embodiment of a control system of the
system of FIG. 1A;
[0011] FIG. 1C shows another system for chemical deposition,
according to embodiments of the disclosure;
[0012] FIGS. 2A to 2B show operation of a sensor assembly according
to embodiments of the disclosure;
[0013] FIGS. 3A and 3B illustrate exemplary signals collected by
the sensor assembly of FIG. 2A;
[0014] FIG. 4 shows a graphical depiction of various outputs of a
control system, in accordance with embodiments of the
disclosure;
[0015] FIG. 5 is a composite graph depicting precursor flux and
integrated flux over time, according to some embodiments;
[0016] FIG. 6A, FIG. 6B, FIG. 6C, and FIG. 6D are exemplary graphs
that illustrate the relationship between integrated flux or related
entities and operating parameters of a system, in accordance with
embodiments of the disclosure;
[0017] FIG. 7 illustrates integrated precursor flux behavior as a
function of time, with and without temperature compensation, in
accordance with embodiments of the disclosure;
[0018] FIG. 8 presents an exemplary process flow according to
embodiments of the disclosure;
[0019] FIG. 9A presents an exemplary process flow according to
embodiments of the disclosure; and
[0020] FIG. 9B presents a model system according to embodiments of
the disclosure.
[0021] The drawings are not necessarily to scale. The drawings are
merely representations, not intended to portray specific parameters
of the disclosure. The drawings are intended to depict exemplary
embodiments of the disclosure, and therefore are not be considered
as limiting in scope. In the drawings, like numbering represents
like elements.
[0022] Furthermore, certain elements in some of the figures may be
omitted, or illustrated not-to-scale, for illustrative clarity. The
cross-sectional views may be in the form of "slices", or
"near-sighted" cross-sectional views, omitting certain background
lines otherwise visible in a "true" cross-sectional view, for
illustrative clarity. Furthermore, for clarity, some reference
numbers may be omitted in certain drawings.
DETAILED DESCRIPTION
[0023] The present embodiments will now be described more fully
hereinafter with reference to the accompanying drawings, where some
embodiments are shown. The subject matter of the present disclosure
may be embodied in many different forms and are not to be construed
as limited to the embodiments set forth herein. These embodiments
are provided so this disclosure will be thorough and complete, and
will fully convey the scope of the subject matter to those skilled
in the art. In the drawings, like numbers refer to like elements
throughout.
[0024] The embodiments described herein provide novel processing
and control of precursors in chemical deposition processes, such as
atomic layer deposition (ALD) processes. ALD generally involves
sequential exposure to two or more reactants to deposit a given
monolayer of material. In various embodiments, a chemical
deposition process may be performed to deposit any appropriate
material, including oxides, nitride, carbides, dielectrics,
semiconductors, or metal. The chemical deposition process may
involve control of precursor flow as detailed in the embodiments to
follow.
[0025] Turning now to FIG. 1A, there is shown a system 100 for
chemical deposition, according to embodiments of the disclosure.
The system 100 involves use of at least one precursor, generally
provided as a gaseous species to process chamber, referred to as
deposition chamber 110. The system 100 may be employed to perform
chemical vapor deposition (CVD) or atomic layer deposition (ALD) in
different embodiments. The embodiments are not limited in this
context. The system 100 includes a source, such as ampoule 104,
where the ampoule 104 may contain a solid, liquid or gas. The
ampoule 104 may be maintained at an elevated temperature to
generate a gaseous species, which species may be referred to herein
as a precursor. The ampoule 104 may be coupled to a delivery system
114, configured to conduct at least one gaseous species, and in
some cases, multiple gaseous species, to the deposition chamber
110, as in known CVD or ALD systems. For example, the delivery
system 114 may include a plurality of gas lines, valves, and flow
controllers. At least a portion of the delivery system 114 may be
contained within a hot chamber 106, where the hot chamber 106 is
maintained at an elevated temperature with respect to the ampoule
104, ensuring precursor(s) remain in a gaseous state, at least
until entering deposition chamber 110.
[0026] The system 100 may further include a sensor assembly 108,
arranged to monitor flow of at least one precursor between the
ampoule 104 and deposition chamber 110. The sensor assembly 108 may
be coupled to a control system 112, where the control system 112
may output information or signals to a user, as well as send
control signals for controlling operating parameters of system 100,
including temperature, precursor flow, and so forth. Details of an
embodiment of the control system 112 are shown in FIG. 1B and
discussed further below.
[0027] In accordance with embodiments of the disclosure, the
control system 112 may be implemented in a combination of hardware
and software. The control system 112 may comprise various hardware
elements, software elements, or a combination of hardware/software.
Examples of hardware elements may include devices, logic devices,
components, processors, microprocessors, circuits, processor
circuits, circuit elements (e.g., transistors, resistors,
capacitors, inductors, and so forth), integrated circuits,
application specific integrated circuits (ASIC), and programmable
logic devices (PLD). Examples of hardware elements may also include
digital signal processors (DSP), field programmable gate array
(FPGA), memory units, logic gates, registers, semiconductor device,
chips, microchips, chip sets, and so forth. Examples of software
elements may include software components, programs, applications,
computer programs, application programs, system programs, software
development programs, machine programs, operating system software,
middleware, firmware, software modules, routines, subroutines, and
functions. Examples of software elements may also include methods,
procedures, software interfaces, application program interfaces
(API), instruction sets, computing code, computer code, code
segments, computer code segments, words, values, symbols, or any
combination thereof. Determining whether an embodiment is
implemented using hardware elements and/or software elements may
vary in accordance with any number of factors, such as desired
computational rate, power levels, heat tolerances, processing cycle
budget, input data rates, output data rates, memory resources, data
bus speeds and other design or performance constraints, as desired
for a given implementation.
[0028] As an example, the control system 112 may include various
hardware outputs, which outputs may be embodied as signals for
controlling other components of system 100, may be output on user
interfaces, or output in other manner. In some examples, the
hardware outputs may be employed as inputs by control system 112 to
control components of system 100, as detailed below. Table I
includes a listing of exemplary hardware outputs according to some
embodiments of the disclosure. In this example, temperature, such
as temperature of the ampoule 104, may be output, as well as gas
pressure, precursor concentration, and a health monitor (reference
signal).
TABLE-US-00001 TABLE I Output Temperature (C.) Pressure (T)
Concentration (%) Health Monitor (a.u.)
[0029] These outputs may be collected periodically, intermittently,
and in synchronicity, or separately (in time) from one another.
[0030] Turning now to Table II. there are shown a set of operations
or capabilities where the capabilities may be performed by the
control system 112, according to some embodiments of the
disclosure, where these capabilities are detailed in the discussion
to follow.
TABLE-US-00002 TABLE II Capability Purpose Chamber Flux (umol/sec)
Model for precursor flux delivered to wafer Integrated Ch. Flux
(umol) Total precursor flux over a wafer Ampoule Integrated flux
Lifetime flux of precursor ampoule End of life Detection Signals
ampoule change needed Fault detection Detect and classify faults
(e.g. clogs) Ampoule T compensation Feedback loop for dynamic T
adjust
[0031] Turning now to FIG. 1B, there is shown another depiction of
the control system 112. In various embodiments, the control system
112, may include a processor 150, such as a known type of
microprocessor, dedicated semiconductor processor chip, general
purpose semiconductor processor chip, or similar device. The
control system 112 may further include a memory or memory unit 160,
coupled to the processor 150, where the memory unit 160 contains a
flux control routine 162, as described below. The flux control
routine 162 may be operative on the processor 150 to control
precursor flux or precursor flow in the system 100, as detailed
below. In some embodiments, the flux control routine 162 may
include an end-of-life processor 164, an excursion processor 166,
and a clog-detection processor 168, a temperature control processor
170, and a flux calculation processor 172, where implementation of
these processors is described with respect to the embodiments
discussed below.
[0032] The memory unit 160 may comprise an article of manufacture.
In one embodiment, the memory unit 160 may comprise any
non-transitory computer readable medium or machine readable medium,
such as an optical, magnetic or semiconductor storage. The storage
medium may store various types of computer executable instructions
to implement one or more of logic flows described herein. Examples
of a computer readable or machine-readable storage medium may
include any tangible media capable of storing electronic data,
including volatile memory or non-volatile memory, removable or
non-removable memory, erasable or non-erasable memory, writeable or
re-writeable memory, and so forth. Examples of computer executable
instructions may include any suitable type of code, such as source
code, compiled code, interpreted code, executable code, static
code, dynamic code, object-oriented code, visual code, and the
like. The embodiments are not limited in this context.
[0033] The memory unit 160 may include a system database 180,
including parameters for operating the system 100. Exemplary
parameters include, for example, a baseline ampoule side
temperature and a baseline ampoule bottom temperature, where these
parameters may be set as starting points for control operations to
be performed, such as for temperature compensation to be performed.
Other parameters subject to control may include flow rate as well
as deposition time. Additional parameters, which parameters may
also be stored in system database 180, may be employed to assign
limits to ensure the temperature of a process stays within a safe
range. Among these parameters are ampoule side temperature minimum,
ampoule side temperature maximum, ampoule bottom temperature
minimum, ampoule bottom temperature maximum, hot chamber
temperature, and precursor degradation temperature.
[0034] Turning now to FIG. 1C, there is shown a system 118 for
chemical deposition, according to further embodiments of the
disclosure. The system 118 involves use of at multiple precursors,
generally provided as a gaseous species to process chamber,
referred to as deposition chamber 110. The system 118 may operate
similarly to system 100, while the system 118 includes a first
ampoule 104A for a first precursor and a second ampoule 104B for a
second precursor. The control system 112 may act to independently
control the first ampoule 104A and the second ampoule 104B
according to the principles detailed in the discussion to follow.
This configuration facilitates control of two different precursors
where the different precursors may be used form different
condensing species in a CVD or ALD process. In other embodiments, a
system, such as system 100 or system 118, may be coupled with a gas
flow apparatus supplying a gaseous precursor from a gas source to a
deposition chamber, such as NH.sub.3 or H.sub.2. As such, a CVD or
ALD system may employ the gas source to deliver the gaseous
precursor, while at least one other precursor is delivered from an
ampoule under active control according the embodiments described
herein.
[0035] In various embodiments, the sensor assembly 108 may be
arranged with any suitable components for monitoring a precursor,
including electromagnetic radiation, acoustic signals, and so
forth. The embodiments are not limited in this context. The sensor
assembly 108 may determine precursor flux or concentration by
measuring a change in signal intensity of an appropriate signal
transmitted through the sensor assembly 108, as detailed below.
Turning to FIG. 2A and FIG. 2B, there is shown principle of
operation of the sensor assembly 108, in accordance with some
embodiments of the disclosure. The sensor assembly 108 may include
a light source 120, such as an infrared, visible, or ultraviolet
light source, and a detector 122, facing the light source 120. The
detector 122 may be any detector, appropriate for the type of
radiation source used for light source 120. The sensor assembly 108
may further include a chamber, shown as cell 124, where the cell
124 is arranged to receive a precursor 126 and to conduct the
precursor 126, as the precursor 126 travels from the ampoule 104 to
the deposition chamber 110. When the precursor 126 is absent from
the cell 124, as in FIG. 2A, the detector 122 may register a
signal, such as the background signal 130. The background signal
130 represents transmitted (detected) intensity as a function of
wavelength of the radiation from light source 120. In some
embodiments, the background signal 130 may be featureless, such as
shown in FIG. 3A. When precursor 126 is present in the cell 124,
the precursor may absorb radiation emitted by the light source 120,
wherein the detector 122 registers a precursor signal 134. For
clarity of explanation, the precursor signal 134 is shown to
exhibit a peak 136, while the precursor signal 134 may include a
multiplicity of features, including multiple peaks in some
embodiments. Notably, the presence of the precursor 126 in the cell
124 may reduce the overall intensity of detected radiation in
precursor signal 134, as opposed to background signal 130. As
detailed below, in various embodiments, the recording of the
background signal 130, as well as the monitoring of the precursor
signal 134, over a plurality of instances, is employed to control
operation of a deposition process.
[0036] As further shown in FIGS. 3A and 3B the sensor assembly may
also collect a reference signal 132, where the reference signal 132
indicates the relative changes inn detector performance of the
detector 122 over time. Changes in intensity of the reference
signal 132 may be indicative of degradation in performance of the
detector 122. By collecting the reference signal 132 at various
instances, in conjunction with measuring the background signal 130,
and precursor signal 134, the amount of precursor 126 may be
accurately determined over time. In particular, the light
absorption by precursor 126 may be directly proportional to the
partial pressure of the precursor 126 in the cell 124. As such,
physical modelling may be employed to calculate precursor flux at
multiple instances, based upon the repeated measurement of a
precursor signal 134, facilitating better control of chemical
deposition processes involving the precursor 126. In addition to
measuring precursor flux, the cell pressure, such as total
pressure, in the cell 124 may also be measured.
[0037] Turning now to FIG. 4 there is shown a graphical depiction
of various outputs of the control system 112, in accordance with
embodiments of the disclosure. The curve 402 illustrates
temperature of the ampoule 104 as a function of time. In this
example, the temperature is relatively constant as a function of
time. During a deposition process, the changing of temperature may
result in the changing of precursor flux by heating the ampoule 104
to generate a higher partial pressure of precursor.
[0038] The curve 406 represents the reference intensity of a
detector, for example, indicating the detector continues to
function the same over the time period measured. The health of a
sensor may be determined from comparison of a reference intensity
value taken at a certain time, with respect to the reference
intensity at a current time. Thus, if the value of the reference
intensity deteriorates substantially over time, this deterioration
may be deemed an indication of bad health of the sensor. The curve
408 represents the pressure in a chamber as a function of time,
while the curve 404 represents the concentration of a precursor as
a function of time. As shown, the precursor is delivered in a
series of pulses of concentration 412, resulting in corresponding
pulses of pressure.
[0039] Turning now to FIG. 5 there is shown a curve 502,
representing the precursor flux transported through a system, such
as the flux of a precursor conducted through the sensor assembly
108. In accordance with various embodiments of the disclosure, a
physics-based calculation is performed to determine precursor flux,
where the calculation does not require a constant pressure or
temperature at a sensor, such as detector 122, or within the
gaslines used to conduct the precursor from an ampoule to
deposition chamber. In the example of FIG. 5, the curve 502
exhibits a series of pulses 506, representing pulses in precursor
flux, generated by pulses of the precursor. The curve 504
represents the integrated flux of precursor over time, representing
a sum of the pulses 506. The curve 504 may be indicative of the
amount of precursor delivered to a deposition chamber at any given
instance in time. A sensor assembly, such as sensor assembly 108,
may be maintained in an operational state during the chemical
deposition process, so any pulse 506 is recorded, wherein the
integrated flux at a given instance represents the sum of all the
flux pulses recorded to that point.
[0040] While the example of FIG. 4 and FIG. 5 are directed to
precursor flux monitoring, in other embodiments, byproducts or
secondary precursors may be monitored. For example, in some
chemical systems, a precursor may decompose during transport,
wherein the precursor as well as the byproduct of decomposition may
pass through a detector cell. Accordingly, by adding an additional
detector, so a precursor detector, byproduct detector, and health
detector are present, such a detector system may be used to
determine relative flow of a precursor vs a byproduct.
[0041] The determination of precursor flux and integrated precursor
flux may be used to monitor, characterize, or control a deposition
process in accordance with various embodiments of the disclosure.
FIG. 6A, FIG. 6B, FIG. 6C, and FIG. 6D are exemplary graphs
illustrating the relationship between integrated flux or related
entities and certain experimental or operating parameters of a
system, such as the system 100. The data shown represent the
deposition of Cobalt using a (3,3-Dimethyl-1-butyne)
dicobalthexacarbonyl (CCTBA) precursor. This chemical system is
merely exemplary, and in other embodiments other metal organic or
halogen species may be used to deposit cobalt, or other metal.
[0042] In FIG. 6A, there is shown the relationship between
integrated flux and deposition time, for measurement collected over
a deposition time window as shown. The integrated flux is
determined using a sensor assembly as described above. As shown,
the integrated flux shows a good linear fit with deposition time.
FIG. 6B depicts the relationship between carrier gas flow rate and
integrated flux, again showing linear behavior over a carrier flow
rate between 100 sccm and 400 sccm. FIG. 6C depicts the
relationship between ampoule bottom temperature and integrated
flux, again showing linear behavior over a temperature range
between 32 C and 38 C.
[0043] In FIG. 6D, there is shown the measured thickness of a
deposit as a function of flux, showing a linear relation for two
different units (alpha and beta). The data toward the right
represents data collected toward the beginning of the ampoule life
while a decrease in flux and deposit thickness occurs as the
ampoule precursor material is consumed.
[0044] Thus, the data shown in FIGS. 6A-6D illustrate how
integrated flux in a chemical deposition system such as cobalt is
sensitive to parameters including deposition time, carrier flow
rate, and ampoule temperature. In other embodiments, dilution flow
of any other flow to a process chamber, the number of deposition
steps, or chamber pressure may be modulated to control precursor
flux.
[0045] In some embodiments, the information regarding precursor
flux may be used to dynamically control a deposition process, for
example, to achieve process stability and to prevent or counter
drift in a deposition process. FIG. 7 illustrates integrated
precursor flux behavior as a function of time for an atomic layer
deposition system for depositing TaN. The diamond symbols indicate
integrated precursor flux as a function of time where no
temperature adjustment is performed during a series of depositions,
for up to approximately wafer 4500. A lower limit and an upper
limit are shown by the horizontal dashed lines. As illustrated, the
precursor flux when temperature is not adjusted remains generally
between the upper limit and lower limit up to approximately the
instance of processing of wafer 1500, and decreases substantially
below the lower limit at higher wafer numbers. Given the upper
limit and lower limit may represent a target operating range, the
results illustrate the uncompensated flow of precursor is unable to
maintain the process within the target operating range above wafer
1500. The triangle symbols represent integrated precursor flux as a
function of time where temperature adjustment is performed during a
series of depositions, in accordance with embodiments of the
disclosure. In this set of data, the temperature of a precursor
ampoule may be adjusted in accordance with procedures detailed
below. As a result, the integrated flux is maintained over the
entirety of a range measured (up to wafer 3500).
[0046] Turning now to FIG. 8, there is shown a process flow 800, in
accordance with embodiments of the disclosure. The process flow 800
may be implemented by the processors as described above, and as
indicated in the figure. Notably, some operations may be performed
by more than one processor. At block 802, an integrated precursor
flux is set for a given deposition process. A setpoint may be
established, where the integrated flux is to be determined based
upon measurements of a precursor using a sensor assembly in
accordance with the embodiments described above. In various
embodiments, multiple parameters may be set or monitored. For
example, a baseline ampoule side temperature and a baseline ampoule
bottom temperature may be set as starting points for temperature
compensation to be performed. Additional parameters may be employed
to assign limits to ensure the temperature of a process stays
within a safe range. Among these parameters are ampoule side
temperature minimum, ampoule side temperature maximum, ampoule
bottom temperature minimum, ampoule bottom temperature maximum, hot
chamber temperature, and precursor degradation temperature.
[0047] At block 804, a substrate or wafer is processed according to
the given deposition process. The flow proceeds to block 806, where
an integrated chamber flux is calculated for the precursor, as
represented, for example, at curve 504. At block 808, a sensor such
as the detector 122 is checked to see if correct readings are being
made and a baseline reading is correct. If a determination is made
wherein the sensor needs adjusting the flow proceeds to block 810,
where in one mode a signal is sent to a user indicating the sensor
needs adjusting, while in another mode, an adjustment to the sensor
is performed automatically. The flow then returns to block 804. If,
at block 808, the sensor does not need adjusting, the flow proceeds
to block 812, where the integrated precursor flux from block 806 is
checked against fixed control limits. If the precursor flux
indicates the process is under control or within control limits,
the flow proceeds to block 814, where no adjustment is made to
ampoule temperature. The flow then returns to block 804 where a
wafer is processed while not having adjusted ampoule temperature
for the precursor.
[0048] In some embodiments, as exemplified in process flow 800, two
sets of limits may be specified, such as fault limits and waring
limits. When a warning limit is exceeded, this condition triggers a
temperature update. Fault limits are broader, wherein when a fault
limit is exceeded, this condition indicates something has changed
in the system (not the gradual drift expected over an ampoule
lifetime) and additional action is required.
[0049] In the process flow 800, if, at block 812, a fault condition
(fault band condition) is detected, the flow proceeds to block 816,
where an ampoule idle time is checked. The flow then returns to
block 814 if a first wafer is being processed. If a first wafer is
not being processed, the flow proceeds to block 818, where fault
detection and classification is performed. The flow then proceeds
to block 820, where a notification signal is sent to notify a user
an excursion has been detected. The flow may then proceed to block
814. In different implementations, processing may be stopped or a
user notified while processing continues via block 804.
[0050] If, at block 812, a warning band condition is determined,
the flow proceeds to block 822, where an error calculation is
performed.
[0051] In different embodiments, warning and fault limits may be
assigned by a user or alternatively may be calculated automatically
in a software routine. In some examples, the limits represent a
given number of standard deviations from the mean of a sample
set.
[0052] In particular, the error calculation at block 822 may
involve control limits, determined experimentally, based upon
sensor noise and thickness sensitivity. The error value calculated
may be based upon a subtraction of the integrated flux from an
upper control limit (UCL) or lower control limit (LCL). The flow
then proceeds to block 824.
[0053] At block 824, a temperature increment .DELTA.T is
determined. In one embodiment, the temperature increment may be
calculated based upon .DELTA.T=P* +D*d /dt+I*.intg. /dt, where P, I
and D are the proportional, integral, and derivative gains. In one
instance, P, D, and I may be experimentally determined from tuning
experiments. The flow then proceeds to block 826.
[0054] At block 826, the temperature increment, .DELTA.T, is
rounded to a nearest level, such as to the nearest 0.5.degree. C.
The flow then proceeds to block 828, where new setpoints are
calculated for side and bottom temperatures of an ampoule, wherein
T.sub.K=T.sub.K-1+.DELTA.T, where T.sub.K is the temperature at
time k, and T.sub.k-1 is the previous temperature setpoint. The
flow then proceeds to block 830.
[0055] At block 830, where the setpoints determined at block 828
are checked against current temperature limits for the ampoule
containing the precursor. If, at block 830, the setpoints are
within the limits, the flow then proceeds to block 832. These
limits may include the aforementioned ampoule side temperature
minimum, ampoule side temperature maximum, ampoule bottom
temperature minimum, ampoule bottom temperature maximum, hot
chamber temperature, and precursor degradation temperature.
[0056] At block 832, the ampoule temperature setpoints are updated
based upon the new setpoints determined at block 828. The flow then
proceeds to block 834 to wait for the precursor flux to stabilize,
and then returns to block 804.
[0057] If, at block 830, the setpoints are not within the limits,
the flow proceeds to block 836, where the end of life of the
precursor ampoule is checked. At block 836, if a determination is
made wherein the ampoule is at an end-of-ampoule life condition,
the flow proceeds to block 838, where a signal is sent to notify a
user for preventative maintenance. The flow then proceeds to block
840, where a temperature increment is recalculated based upon a
most conservative limit. The most conservative limit may represent
the lowest of the applicable maximum temperatures or highest of the
applicable minimum temperatures. The flow then returns to block
828. If, at block 836, a determination is made wherein the ampoule
is not at end of life, the flow proceeds directly to block 840. The
end-of-life determination may be made based upon when temperature
compensation is no longer able to maintain a deposition process
within acceptable process conditions.
[0058] Turning now to FIG. 9A there is shown a process flow 900
according to additional embodiments of the disclosure. The process
flow 900 may be implemented by the clog-detection processor 168,
and may be used to determine the presence of clogs and clog
location within a delivery system for chemical deposition. A model
delivery system 930, including precursor ampoule 932 and sensor
assembly 934, are shown in block form in FIG. 9B. Turning to
process flow 900, at block 902, a determination is made as to
whether a transducer pressure in a gasline delivering a precursor
is too high. The transducer pressure may be measured just
downstream of a carrier mass flow controller in the gas line. An
indication of "too high" may be determined statistically. A set of
"good" recipes may be employed to determine the expected mean and
standard deviation (sigma), wherein a deviation on the order of 3
sigma is used to determine if the pressure is high (depending on
sample size and acceptable confidence level). If not, the flow
proceeds to block 904, indicating no clog in a gasline is detected.
If, at block 902, the transducer pressure is high, the flow
proceeds to block 906, where a determination is made if the sensor
assembly 934 pressure is too high. If so, the flow proceeds to
block 908, where a signal is sent indicating a clog is detected
downstream of the sensor assembly 934. If the pressure is not too
high in the sensor assembly 934, the flow proceeds to block
910.
[0059] At block 910, a determination is made if the transducer
pressure is high in a bypass mode, shown by position 4 in FIG. 9B.
If not, the flow proceeds to block 912 where a determination is
made as to whether precursor flux is low. The determination of
whether the precursor flux is low may be made by measuring the
precursor flux at the sensor assembly 934. In particular examples,
the measured precursor flux is compared to "good" data using
statistical approaches including mean and standard deviation. If,
at block 912, the precursor flux is not low, the flow proceeds to
block 914, where a signal is sent indicating a clog exists at the
precursor ampoule 932 inlet, as shown by position 2. If, at block
912, the precursor flux is determined to be low, then the flow
proceeds to block 916, where a signal is sent to indicate a clog is
present at the precursor ampoule 932 outlet, as indicated by
position 3.
[0060] If, at block 910, a determination is made wherein the
transducer pressure is high in bypass mode, the flow proceeds to
block 918, where a determination is made as to whether the
precursor flux is low. If not, the flow proceeds to block 920,
where a signal is generated indicating a clog exists upstream of
the precursor ampoule 932 inlet, as indicated by position 1. If so,
the flow proceeds to block 922, where a signal is sent indicating a
clog between the precursor ampoule 932 outlet and sensor assembly
934, as indicated by position 4.
[0061] In sum, the present embodiments provide the advantages of
the ability to determine precursor flux during operation of a
chemical deposition system, to determine such changes in precursor
flux in real time, to dynamically adjust operating parameters such
as ampoule temperature in real time, in order to maintain precursor
flow within acceptable limits. Other advantages include the ability
to determine or predict end-of-life of a precursor ampoule so
replacement need not take place before corrections cannot be made
to maintain the precursor flow within limits. Further advantages
include the ability to determine the presence of clogs in multiple
different locations of a precursor delivery system.
[0062] The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Furthermore, the present disclosure has been described
herein in the context of a particular implementation in a
particular environment for a particular purpose. Those of ordinary
skill in the art will recognize the usefulness is not limited
thereto and the present disclosure may be beneficially implemented
in any number of environments for any number of purposes. Thus, the
claims set forth below are to be construed in view of the full
breadth and spirit of the present disclosure as described
herein.
* * * * *